The glyceryl monoesters, or monoglycerides, are all prepared from glycerin. Most are also prepared from fatty acids or fatty acid derivatives. Some of these fatty acids may come from refined vegetable oils For example, Glyceryl Linolenate is produced from glycerin and linoleic acid, which can be made from sunflower oil. Glyceryl Polyacrylate is the ester of glycerin and polyacrylic acid.

CIR Safety Review: The safety of the 43 glyceryl monoesters was reviewed in one report because these ingredient have similare structures. In addition, many of the fatty acids that are included in these ingredients have been previously reviewed by the CIR Expert Panel and found safe for use. Glyceryl Laurate, Glyceryl Isostearate, and Glyceryl Citrate/Lactate/ Linoleate/Oleate were not classified as ocular irritants.

Undiluted glyceryl monoesters may produce minor skin irritation, especially in abraded skin, but in general these ingredients were not irritating at concentrations used in cosmetics and personal care products. Glyceryl monoesters were not sensitizers, except that Glyceryl Rosinate and Hydrogenated Glyceryl Rosinate may contain residual rosin which can cause allergic reactions. These ingredients were not photosensitizers.

Glyceryl Citrate/Lactate/Linoleate/Oleate was not mutagenic in bacteria. Glyceryl Laurate exhibited antitumor activity and Glyceryl Stearate was negative in a tumor promotion assay. Glyceryl Laurate enhanced the penetration of drugs through human skin and hairless skin in vitro and was described as having a wide spectrum of antimicrobial activity. Glyceryl monoesters have little acute or short-term toxicity, and no toxicity was noted following chronic administration of a mixture consisting mostly of glyceryl di-and mono- esters.

At concentrations higher than used in cosmetics and personal care products, Glyceryl Laurate did cause moderate erythema in human repeat insult patch studies, but the other Glyceryl Monoesters tested failed to produce any significant positive reactions. Glyceryl Rosinate was irritating to skin at 50%, but did not produce sensitization in clinical tests at concentrations up to 10% when covered with semi-occluded patches. There was reported use of Glyceryl Rosinate at 12% in mascara, which was higher than the concentration in the clinical testing. It was reasoned that the available data supported the safety of this use because there would be minimal contact with the skin and no occlusion.

The safety of Arachidonic Acid was not documented and substantiated for cosmetic product use. Therefore, the CIR Expert Panel also concluded that the data were insufficient to support the safety of Glyceryl Arachidonate. The following data were requested: dermal absorption data; based on the results of absorption studies, data on immune system effects, carcinogenicity and phtotsensitization, and irritation, sensitization and photosensitization may be needed.

Glyceryl monoesters are not pure monoesters, but are mixtures with mono-, di-, and tri-esters. Glyceryl monoesters are metabolized to free fatty acids and glycerol, both of which are available for the resynthesis of triglycerides. In cosmetics and personal care products, glyceryl monoesters are used mostly as skin conditioning agents - emollients and/or surfactant - emulsifying agents.

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